This invention relates to a pin tumbler lock and has been devised particularly though not solely to allow the barrel of the lock to be diecast in a single operation without the necessity for further machining.
In the past the barrels for pin tumbler locks have been manufactured by machining the barrel from a brass blank by turning and broaching drilling the guide channels for the pins and turning a circlip groove. The barrel is machined by broaching to form an axial channel having a plurality of axial grooves adapted to receive the key into the barrel of the lock. The axial channel formed by machining intersects with the guide channels drilled for the radially slidable locking pins so that the teeth of the key can move the pins through the desired length to free the barrel for rotation within the cylinder of the lock. This fully machined method of manufacture is relatively expensive, it requires the use of several items of expensive machinery and more importantly it requires the careful setting and maintenance of many metal removing tools. From a manufacturing and product reliability point of view the method is relatively poor.
In a few instances pin tumbler barrels have been partly cast by casting the general barrel shape with the guide channels partly cast and in particular cast in the portion which does not intersect the longitudinal key slot.
The key slot would be cast by employing a longitudinal core which would project the length of the key way, but using this method the pin channels still need to be drilled and the long key way core is susceptable to damage and other casting problems.